1. Field Of The Invention
The present invention deals with the field of electrical circuit breakers adapted to carry normal current loads therein and including two current interrupting means. The first current interrupting means is responsive to a persistent low level overcurrent which achieves thermal tripping of the circuit breaker. The second tripping means is a magnetic tripping means which is responsive to a more instantaneous higher level of current overflow through the circuit breaker for interrupting flow therethrough. The breaker of the present invention is particularly responsive to reduce the level of overcurrents to which the magnetic tripping assembly is responsive.
2. Description Of The Prior Art
Numerous prior art devices have been designed for construction of electrical circuit breakers somewhat similar to the present design such as U.S. Pat. No. 3,152,232 patented Oct. 6, 1964 to J. Leonard on a Circuit Breaker Having Bimetal Rigidly Secured To Cradle; U.S. Pat. No. 3,161,747 patented Dec. 15, 1964 to T. Cole on an Automatic Circuit Breaker Having A Combined Latch And Contact Unit Pivoted To A Contact Carrier; U.S. Pat. No. 3,171,921 patented Mar. 2, 1965 to W. Woods on a Circuit Breaker Operating Mechanism; U.S. Pat. No. 3,200,217 patented Aug. 10, 1965 to E. Bullis, Jr. on a Circuit Breaker With Thermal And Magnetic Trip Means; U.S. Pat. No. 3,555,468 patented Jan. 12, 1971 to F. Myers on a Combined Thermal-Magnetic Trip Means For Circuit Breakers; U.S. Pat. No. 4,085,393 patented Apr. 18, 1978 to A. Grenier on a Circuit Breaker; U.S. Pat. No. 4,260,969 patented Apr. 7, 1981 to W. Troebel et al on a Low Voltage Circuit Breaker With An Electromagnetic Tripping Device; U.S. Pat. No. 4,284,968 patented Aug. 18, 1981 to S. Denoyelle et al on an Adjustable Electromagnetic Tripping Mechanism For A Circuit-Breaker; U.S. Pat. No. 4,683,451 patented Jul. 28, 1987 to K. Grunert et al on a Circuit Breaker With Trip Delay Magnetic Circuit; U.S. Pat. No. 4,868,529 patented Sep. 19, 1989 to T. Holland on a Circuit Breaker Armature Latch With Control Leg; U.S. Pat. No. 4,933,653 patented Jun. 12, 1990 to S. Mrenna et al on a Circuit Breaker With Low Current Magnetic Trip; U.S. Pat. No. 4,951,015 patented Aug. 21, 1990 to J. Shea et al on a Circuit Breaker With Moving Magnetic Core For Low Current Magnetic Trip and U.S. Pat. No. 4,983,939 patented Jan. 8, 1991 to J. Shea et al on a Circuit Breaker With Adjustable Low Magnetic Trip.